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Abstract:

A hemodialysis system including (i) an instrument; (ii) first and second
peristaltic dialysate pumps operated by the instrument; (iii) a cassette
including a rigid structure and first and second dialysate pumping tubes
carried by the rigid structure; and (iv) a mechanism configured to
initially allow the cassette to be accepted by the dialysis instrument
after which the mechanism engages the first and second dialysate pumping
tubes for operation with the first and second peristaltic dialysate
pumps.

Claims:

1. A hemodialysis system comprising: an instrument; first and second
peristaltic dialysate pumps operated by the instrument; a cassette
including a rigid structure and first and second dialysate pumping tubes
carried by the rigid structure; and a mechanism configured to initially
allow the cassette to be accepted by the dialysis instrument after which
the mechanism engages the first and second dialysate pumping tubes for
operation with the first and second peristaltic dialysate pumps.

2. The hemodialysis system of claim 1, wherein the mechanism is
configured to move a member and the first and second dialysate pumping
tubes towards each other to produce the operable engagement.

3. The hemodialysis system of claim 2, wherein the mechanism is
configured to move the member downwardly onto the first and second
dialysate pumping tubes to engage the tubes for operation.

4. The hemodialysis system of claim 1, wherein the mechanism is
configured to move a member away from the first and second peristaltic
dialysate pumps when a door for accepting the cassette is opened.

5. The hemodialysis system of claim 4, wherein the mechanism is
configured to move a member upwardly away from the first and second
peristaltic dialysate pumps when a door for accepting the cassette is
opened.

6. The hemodialysis system of claim 1, wherein the mechanism is
configured to move a member away from the first and second peristaltic
dialysate pumps when a door for accepting the cassette is opened.

7. The hemodialysis system of claim 6, wherein the mechanism is
configured to move a member away from the first and second peristaltic
dialysate pumps after the door is latched closed.

8. The hemodialysis system of claim 1, which includes a motor, and
wherein the mechanism is driven by the motor.

9. The hemodialysis system of claim 1, wherein the mechanism is
configured to engage the first and second dialysate pumping tubes at
substantially the same time.

10. The hemodialysis system of claim 9, wherein the mechanism is cam-
operated to engage the first and second dialysate pumping tubes at the
substantially same time.

11. The hemodialysis system of claim 1, wherein the mechanism is
configured to convert rotational motion to translational motion to engage
the first and second dialysate pumping tubes.

12. The hemodialysis system of claim 11, wherein the mechanism includes a
member that is translated to engage the first and second dialysate
pumping tubes, the member including slots formed by walls that ride along
cams rotated by the mechanism.

13. A hemodialysis system comprising: an instrument; first and second
peristaltic dialysate pumps operated by the instrument; a cassette
including a rigid structure and first and second dialysate pumping tubes
carried by the rigid structure; and a mechanism configured to initially
allow the cassette to be loaded onto a moveable platform of the dialysis
instrument, after which the moveable platform and the mechanism are moved
so that the mechanism engages the first and second dialysate pumping
tubes for operation with the first and second peristaltic dialysate
pumps.

14. The hemodialysis system of claim 13, wherein the platform is a door
connected moveably to the instrument.

15. The hemodialysis system of claim 13, wherein the mechanism is
configured to move a member and the first and second dialysate pumping
tubes towards each other to produce the operable engagement.

16. The hemodialysis system of claim 13, wherein the instrument provides
a blood circuit, a dialysate circuit operated by the first and second
peristaltic dialysate pumps, and a dialyzer placed in communication with
the blood circuit and the dialysate circuit, the system further
configured to operate a priming sequence in which (i) dialysate is used
to prime a first portion of the dialysate circuit and (ii) a
physiologically compatible solution, other than dialysate, is used to
prime a second portion of the dialysate circuit, the dialyzer and the
blood circuit.

17. The hemodialysis machine of claim 16, the first portion of the
dialysate circuit including a recirculation loop primed by at least one
of the first and second peristaltic dialysate pumps.

18. The hemodialysis machine of claim 17, the second portion of the
dialysate circuit located at least substantially between the
recirculation loop and the dialyzer.

19. The hemodialysis machine of claim 18, the second portion of the
dialysate circuit primed by at least one of a blood pump and a downstream
one of the peristaltic dialysate pumps.

20. A method for setting up a hemodialysis treatment comprising:
retracting a peristaltic tube engager to facilitate the loading of a
fluid pumping cassette into a dialysis instrument; enabling a door of the
dialysis instrument to be opened to load the fluid pumping cassette into
the dialysis instrument; and moving the peristaltic tube engager to
engage multiple peristaltic pumping tubes of the fluid pumping cassette.

21. The method of claim 20, wherein the retracting occurs when the door
is opened.

22. The method of claim 20, wherein the moving occurs after the door is
closed.

23. The method of claim 20, which includes enabling the fluid pumping
cassette to be loaded into the door.

24. The method of claim 20, which includes providing the peristaltic tube
engager as a separate structure from a structure that accepts the fluid
pumping cassette.

Description:

PRIORITY

[0001] This application claims priority to and the benefit as a
continuation of U.S. Pat. Ser. No. 12/257,014, entitled "Personal
Hemodialysis System", filed Oct. 23, 2008, which claims priority to U.S.
Provisional patent application No. 60/982,323, entitled "Personal
Hemodialysis System", filed Oct. 24, 2007, the contents of each of which
are incorporated herein by reference and relied upon.

BACKGROUND

[0002] The present disclosure relates generally to medical treatments.
More specifically, the present disclosure relates to medical fluid
treatments, such as the treatment of renal failure and fluid removal for
congestive heart failure.

[0003] Hemodialysis ("HD") in general uses diffusion to remove waste
products from a patient's blood. A diffusive gradient that occurs across
the semi-permeable dialyzer between the blood and an electrolyte solution
called dialysate causes diffusion. Hemofiltration ("HF") is an
alternative renal replacement therapy that relies on a convective
transport of toxins from the patient's blood. This therapy is
accomplished by adding substitution or replacement fluid to the
extracorporeal circuit during treatment (typically ten to ninety liters
of such fluid). That substitution fluid and the fluid accumulated by the
patient in between treatments is ultrafiltered over the course of the HF
treatment, providing a convective transport mechanism that is
particularly beneficial in removing middle and large molecules (in
hemodialysis there is a small amount of waste removed along with the
fluid gained between dialysis sessions, however, the solute drag from the
removal of that ultrafiltrate is not enough to provide convective
clearance).

[0004] Hemodiafiltration ("HDF") is a treatment modality that combines
convective and diffusive clearances. HDF uses dialysate to flow through a
dialyzer, similar to standard hemodialysis, providing diffusive
clearance. In addition, substitution solution is provided directly to the
extracorporeal circuit, providing convective clearance.

[0005] Home hemodialysis ("HHD") is performed in the patient's home. One
drawback of home hemodialysis has been the need for a dedicated water
treatment, which includes equipment, water connection and drainage.
Installing and using those components is a difficult and cumbersome task
that can require a patient's home to be modified. Nevertheless, there are
benefits to daily hemodialysis treatments versus bi- or tri-weekly visits
to a treatment center. In particular, a patient receiving more frequent
treatments removes more toxins and waste products than a patient
receiving less frequent but perhaps longer treatments. Accordingly, there
is a need for an improved HHD system.

SUMMARY

[0006] The present disclosure provides a home hemodialysis ("HHD") system.
In one embodiment, the home system includes a mobile cart and integral
bag manager. A latch is pulled out to unlock door of the system
instrument. The door can be opened to expose a latch hook and peristaltic
pump heads.

[0007] The instrument accepts a disposable unit which in one embodiment is
loaded from above and slid to the right. The disposable unit pivots
towards the machine interface, which allows peristaltic tube loops of the
disposable unit to fit over peristaltic pump heads of the instrument.
Also, supply lines of the disposable unit are passed over individual
pinch valve plungers.

[0008] The pinch valve plungers pinch the supply tubes against a pinch
valve strike plate. The valve assembly is in one embodiment a
motor-driven cam operated pinch valve subassembly. The motor in one
embodiment is a stepper motor.

[0009] The system in one embodiment includes a bellows or bladder that
compresses a cassette against the instrument door using a pressure plate
and gasket. These apparatuses are structured to accommodate an inline
inductive heater provided with the disposable cassette. The bellows is
air actuated in one embodiment. The instrument includes a primary coil
that inductively heats conductive heating disks located within the
cassette, which in turn heat fluid flowing through the cassette.

[0010] A multi-peristaltic pump race retracts and extends in one
embodiment to facilitate loading of the peristaltic tubes of the cassette
onto the peristaltic pump heads. The race is then moved towards the tubes
for operation.

[0011] The system in one embodiment includes a manual blood pump operator,
which allows the patient or caregiver to move the blood pump head
manually.

[0012] The system includes a bag management system having shelves that
fold up, out of the way, and down, sequentially for placement of supply
bags. The system in one embodiment supports up to five, six liter
solution bags. The bags can be dual chamber bags. The shelves in an
embodiment are provided with sensors that allow detection of whether the
bags have been (i) loaded or not and (ii) opened or not for therapy. The
sensors in one embodiment are capacitive sensors placed on opposite ends
of the shelves.

[0013] The disposable cassette in one embodiment connects fluidly to a
heparin syringe for the injection of heparin into the blood circuit. The
syringe fits into a luer connector assembly, which in turn is loaded into
a syringe pump. The assembly is turned in the syringe pump to lock the
syringe in the syringe pump for treatment. The assembly accommodates
large syringes, such as fifty to sixty milliliter syringes, which can
lock directly into the syringe pump. In one embodiment, the heparin line
passes through the side of the cassette. Here, heparin can enter at the
blood pump outlet just prior to the dialyzer inlet.

[0014] The system also includes a retractable saline bag support rod. The
saline in one embodiment connects to the cassette near the heparin line.
A saline valve is located on each side of the blood pump to control the
flow of saline to same.

[0015] A dialyzer inlet pressure sensor interface in one embodiment
doubles as a flow control valve. The cassette can also form an integral
venus air separation chamber.

[0016] Priming is performed in one embodiment via gravity. Gravity primes
the venous line, the arterial line and the air trap (drip chamber).

[0017] In another embodiment, priming is preformed via a combination of
pumping dialysate and a physiologically safe fluid, such as saline. In
particular, a hemodialysis machine can include a blood circuit, a
dialysate circuit, a dialyzer placed in communication with the blood
circuit and the dialysate circuit; and a priming sequence in which
dialysate is used to prime a first portion of the dialysate circuit and a
physiologically compatible solution, other than dialysate, is used to
prime a second portion of the dialysate circuit, the dialyzer and the
blood circuit. The first portion of the dialysate circuit includes a
recirculation loop primed by a dialysate supply pump in one embodiment.
The second portion of the dialysate circuit can then be located at least
substantially between the recirculation loop and the dialyzer, and which
is primed by at least one of a blood pump and a downstream dialysate
pump. In one embodiment, a volumetric balancing unit separates the first
and second portions of the dialysate circuit.

[0018] The cassette in one embodiment uses balance tubes to balance fresh
and spend dialysate flow. The balance tubes have outlets at the top of
the tubes when mounted for operation to allow air to leave the tubes. The
cassette also employs diaphragm valves that operate with a compliance
chamber that seals against backpressure.

[0019] For instance, a hemodialysis machine can include a dialysis
instrument having at least one peristaltic pump actuator and first and
second pneumatic valve actuators. The instrument operates with a
disposable cassette, the disposable cassette including a rigid portion,
with at least one peristaltic pump tube extending from the rigid portion
for operation with the at least one pump actuator. The rigid portion
defines first and second valve chambers in operable connection with the
first and second valve actuators, respectively, the first and second
valve chambers communicating fluidly with each other, at least the first
valve chamber communicating fluidly with a compliance chamber, the
compliance chamber absorbing energy from a pneumatic closing pressure
applied to close the first valve chamber, so as to tend to prevent the
pneumatic closing pressure from opening an existing closure of the second
valve chamber.

[0020] The machine in one embodiment includes a vacuum applied to the
compliance chamber to absorb the energy from the pneumatic closing
pressure applied to close the first valve chamber.

[0021] In the above example, a flexible membrane can be sealed to the
rigid portion, the pneumatic closing pressure applied to the membrane to
close the first valve chamber. Here, the compliance chamber is formed in
part via a portion of the flexible membrane, wherein the flexible
membrane portion is configured to absorb the energy from the pneumatic
closing pressure. The cassette can alternatively include a flexible
diaphragm located on an opposing side of the rigid portion from the
flexible membrane, the compliance chamber formed in part via the flexible
diaphragm, the flexible diaphragm configured to absorb the energy from
the pneumatic closing pressure.

[0022] The disposable cassette can have multiple compliance chambers
operating with different sets of valve chambers. The compliance chamber
aids both upstream and downstream valves. The compliance chamber
overcomes a backpressure applied by the closing of the second valve
chamber to the first valve chamber, to allow the first valve chamber to
close properly.

[0023] In another compliance chamber embodiment, the dialysis instrument
has a pump actuator and first and second valve actuators. A disposable
cassette is operable with the dialysis instrument, the disposable
cassette including a pump portion operable with the pump actuator, the
first and second valve chambers communicating fluidly with each other, at
least the first valve chamber communicating fluidly with a compliance
chamber, the compliance chamber negating a first backpressure due to a
pneumatic closing pressure used to close the first valve chamber to help
to ensure the pneumatic pressure applied to the first valve chamber will
close the first valve chamber against a second backpressure from an
existing closure of the second valve chamber. Here, a pneumatic pressure
applied to the second valve chamber can be the same as the pneumatic
pressure applied to the first valve chamber. The first backpressure would
exist around an outside of a port of the first valve chamber if not for
the compliance chamber, the second backpressure existing inside the port.
As before, the compliance chamber is further configured to tend to
prevent the pneumatic pressure applied to the first valve chamber from
opening the closed second valve chamber. And, the machine in one
embodiment includes a vacuum applied to the compliance chamber to ensure
the pneumatic pressure applied to the first valve chamber will close the
first valve chamber.

[0024] In a further compliance chamber embodiment, the dialysis instrument
has a pump actuator and first and second valve actuators. The disposable
cassette is operable with the dialysis instrument, the disposable
cassette including a pump portion operable with the pump actuator, and
first and second valve chambers operable with the first and second valve
actuators, respectively, the cassette further including a compliance
chamber in fluid communication with the first and second valve chambers,
the compliance chamber defined at least in part by a rigid wall of the
cassette and a diaphragm located on an opposing side of the rigid wall
from the first and second valve chambers. The rigid wall in one
embodiment defines first and second apertures that allow the first and
second valve chambers to communicate fluidly, respectively, with the
compliance chamber. The cassette can include a flexible membrane located
on an opposing side of the cassette from the diaphragm, the membrane for
closing the first and second valve chambers. Again, the compliance
chamber can aid at least one of: (i) maintenance of an existing closure
of the second valve chamber when the first valve chamber is closed; and
(ii) a proper closure of the first valve chamber at a time when the
second valve chamber is already closed. In one embodiment, the aiding is
provided via a vacuum applied to the compliance chamber.

[0025] In still a further compliance chamber embodiment, a dialysis
instrument has a pump actuator and first and second valve actuator. A
disposable cassette is operable with the dialysis instrument, the
disposable cassette including a pump portion operable with the pump
actuator, and first and second valve chambers operable with the first and
second valve actuators, respectively. A compliance chamber is placed in
fluid communication with the first and second valve chambers, the
compliance chamber defined by in part by a flexible membrane used to
close at least one of the first and second valve chambers, the valve
chambers each defining an aperture for fluid communication with the
compliance chamber. The disposable cassette can include a rigid wall, the
first and second valves chambers extending from the rigid wall towards
the flexible membrane, wherein the apertures of the first and second
valve chambers are formed in the rigid wall, and wherein the rigid wall
also forms a third, larger aperture to allow fluid flowing through the
valve chamber apertures to communicate fluidly with the flexible membrane
of the compliance chamber. Again, the compliance chamber aiding at least
one of: (i) maintenance of an existing closure of the second valve
chamber when the first valve chamber is closed; and (ii) a proper closure
of the first valve chamber at a time when the second valve chamber is
already closed. Again, the aiding can be provided via a vacuum applied to
the compliance chamber.

[0026] It is therefore an advantage of the present disclosure to properly
seal valves in fluid communication with one another.

[0027] It is another advantage of the present disclosure to provide an
efficient priming technique that combines the use of dialysate and
another physiologically safe fluid, such as saline.

[0028] Additional features and advantages are described herein, and will
be apparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

[0029]FIG. 1 is a perspective view of one embodiment of a personal home
hemodialysis ("HHD") system having a mobile cart and integral bag
manager.

[0030]FIG. 2 illustrates the system of the present disclosure, in which a
latch is pulled out to unlock a door.

[0031]FIG. 3 illustrates the system of the present disclosure, in which a
door is opened exposing a latch hook and peristaltic pump heads.

[0032] FIG. 4 illustrates one embodiment of the system of the present
disclosure, in which the door is hidden to more clearly show the door
latch.

[0033] FIG. 5 illustrates one embodiment of the system of the present
disclosure, in which a disposable unit is loaded from above and slid to
the right.

[0034]FIG. 6 illustrates one embodiment of the system of the present
disclosure, in which the disposable unit is pivoted forward towards the
interface.

[0035]FIG. 7 illustrates one embodiment of the system of the present
disclosure, in which the disposable unit pivots forward and the tube
loops fit over the peristaltic pump heads.

[0036]FIG. 8 illustrates one embodiment of the system of the present
disclosure, in which the supply lines are placed in operable
communication with individual pinch valve plungers.

[0037]FIG. 9 illustrates one embodiment of the system of the present
disclosure, in which the supply lines are hidden to show pinch valve
plungers.

[0038]FIG. 10 is rear view of one embodiment of the system of the present
disclosure showing a pinch valve strike plate.

[0039]FIG. 11 is a perspective view of one embodiment of a cam operated
pinch valve subassembly operable with the system of the present
disclosure.

[0040]FIG. 12 is another perspective view of the pinch valve subassembly
of FIG. 11.

[0041]FIG. 13 is a perspective view of the pinch valve subassembly of
FIG. 11 with its housing and motor hidden.

[0091]FIG. 65 is a fluid schematic illustrating one embodiment for
closing a venous line clamp, opening a saline valve and rinsing back
blood from the arterial line.

[0092] FIG. 66 is a fluid schematic illustrating one embodiment for
closing an arterial line clamp, opening a saline valve and rinsing back
blood from the venous line.

[0093]FIG. 67A is a perspective view of one embodiment of a disposable
interface subassembly operable with the HHD system of the present
disclosure.

[0094] FIG. 67B is another view of the disposable interface subassembly of
FIG. 67A.

[0095]FIG. 67c is an exploded view of an internal module operable with
the subassembly of FIGS. 67A and 67B.

[0096]FIG. 68 is a perspective view illustrating springs at the four
corners of the subassembly of FIGS. 67A and 67B that retract the internal
module of FIG. 67c.

[0097]FIG. 69 is a perspective view illustrating the backside of one
embodiment of a cassette interface faceplate operable with the HHD system
of the present disclosure.

[0098]FIG. 70 is a perspective view illustrating the backside of one
embodiment of a membrane gasket operable with the HHD system of the
present disclosure.

[0099]FIG. 71 is a perspective view of the internal instrument components
from the backside of the hemodialysis system, showing that there is room
for additional, e.g., electrical, components.

[0100]FIG. 72 is a perspective view of one embodiment of the HHD system
operating in conjunction with an online dialysate generation system.

[0101] FIG. 73A illustrates one embodiment of a diaphragm valve assembly
having a compliance chamber seal against backpressure, which is operable
with the HHD system of the present disclosure.

[0102]FIG. 73B illustrates one embodiment of a valve assembly having
compliance chambers.

[0103]FIG. 74 is a perspective view of a disposable cassette having the
valve assembly of FIGS. 73A and 73B.

[0104] FIG. 75 illustrates one embodiment of a peristaltic pump head sized
to operate with multiple supply lines for mixing different fluids of the
HHD system of the present disclosure.

DETAILED DESCRIPTION

[0105] Referring now to the drawings, FIG. 1 illustrates one embodiment of
a system 10 sitting idle with its dust cover (not illustrated) removed. A
handle 12 for a cart 14 is located in a lowered position to minimize the
space that system 10 consumes. Shelves 16 for the supply bags (shown
below) are also shown in a lowered or "down" position, which minimizes
the height of system 10.

[0106] System 10 is programmed in an introductory state to instruct the
user to open a door 18 shown in FIG. 2. FIG. 2 illustrates a close-up
view of system 10 with a latch 34 pulled out to unlock door 18. Once door
18 is unlocked as seen in FIG. 3, it swings open, e.g., about forty-five
degrees, and is held in the open position by a stop (not seen), so that a
disposable set (shown below) can be loaded or unloaded.

[0107]FIG. 3 illustrates instrument 20 of system 10 with door 18 held in
the open position, exposing multiple peristaltic pump heads 22, a latch
hook 24, inductive heater coil 26 and a slotted area 28 for the blood
lines (not illustrated) to run to and from the patient. Ultrasonic air
bubble detectors and optical blood/saline/air detectors are integrated
into the molded slotted area 28 just above a cutout in the slot for the
venous and arterial line clamps. The cutout located in slotted area 28
accommodates the venous and the arterial line clamps. FIG. 16 shows the
venous and arterial line clamps 76 in the closed position, in which the
clamps extend through a respective cutout. In an alternative embodiment,
the inductive heater coil 26 is retracted into the system to facilitate
loading.

[0108] In FIG. 4, door 18 is not shown for clarity to illustrate latch 34
and latch hook 24, wherein latch 34 mechanically engages latch hook 24 to
hold door 18 closed against the main portion of instrument 20. One
suitable latch assembly is shown and described in FIGS. 11 and 13 of U.S.
Pat. No. 6,261,065, "System and Methods for Control of Pumps Employing
Electrical Field Sensing", the pertinent portions of which are
incorporated herein expressly by reference.

[0109] As seen in FIG. 5, once door 18 has been opened, system 10 prompts
the user to load the disposable set. A cassette 40 of the disposable set
is lowered into instrument 20 and moved to the right (with respect to the
orientation of instrument 20 in FIG. 4). Cassette 40 is loaded starting
at the upper left side of open door 18, so that the patient's blood lines
extending downwardly from cassette 40 do not interfere with the loading
procedure. The patient's left hand can grasp a dialyzer 36 connected to
cassette 40, while the patient's right hand can grasp a tubing bundle 38
formed by the supply and drain lines. Single handed loading is also
possible, e.g., using right hand only grasp bundle 38 to move both
cassette 40 and dialyzer 36.

[0110] As seen in FIGS. 6 and 7, door 18 pivots cassette 40 forward
towards a cassette interface 50 of instrument 20 when an opening 42 in
cassette 40 is located directly over the inductive heater transformer
coil 26. In an alternative embodiment, transformer coil 26 is retracted
to facilitate loading of cassette 40. In such case, coil 26 is then
extended into operating position after cassette 40 is loaded against
interface 50. A bezel (not shown) provides locating stops for stopping
cassette 40 in the vertical and horizontal directions.

[0111] As cassette 40 mates with the cassette interface 50, the
peristaltic pump tubing loops 44 of cassette 40 slip over the vertically
aligned pumping heads 22. A pump race 46 is retracted automatically
upwardly when door 18 is opened to provide clearance between the pump
heads 22 and pump race 26 to facilitate the loading of pump tubing 44 and
cassette 40.

[0112]FIG. 8 illustrates the supply lines 38a to 38e of bundle 38 (number
of supply lines 38 can vary) passing over retracted pinch valves 48.
System 10 also retracts pinch valves 48 automatically when door 18 is
opened to facilitate the loading of bundle 38 and cassette 40 against
interface 50 of instrument 20. System 10 opens and closes pinch valves 48
in a controlled manner, eliminating the need for manual clamps on supply
lines 38a to 38e. FIG. 9 is shown with supply lines 38 removed to more
clearly illustrate pinch valve plungers 48.

[0114] FIGS. 11 and 12 illustrate a pinch valve subassembly 60, in which
three of the five plungers 48 are extended (closed state). Clamp heads 54
are connected to a pinch valve body 62 of subassembly 60. FIG. 13 is
shown with body 62 removed to illustrate springs 56 that spring load
pinch valve plungers 48, e.g., so as to be normally closed. Springs 56
preload pinch valve plungers 48, allowing for variations in the wall
thickness of supply tubes 38. FIG. 13 also illustrates that clamp heads
54 are formed with cam followers 58, which ride on associated cam lobes
62 coupled to a camshaft 64 (FIGS. 11 and 14). A motor 66, e.g., a
stepper motor, is coupled to a drive camshaft 64. FIG. 14 illustrates
that in one embodiment, the individual cam lobes 62 each define apertures
configured fit onto a keyed portion 68 of shaft 64. FIG. 14 further
illustrates the interaction of cam followers 58 and cam lobes 62.

[0115]FIG. 15 illustrates that when cassette 40 is loaded into instrument
20 of system 10, blood lines 72 and 74 exit to the lower left of door
assembly 90 with venous and arterial line clamps 76 (FIG. 16) open
initially. FIG. 16 illustrates that venous and arterial line clamps 76
pinch bloodlines 72 and 74 against housing portion 78 of instrument 20 to
close bloodlines 72 and 74. During normal operation, system 10 operates
clamps 76 independently as needed. FIG. 17 is shown with housing portion
78 and door assembly 90 removed to more fully illustrate venous and
arterial line clamp subassembly 70. A strike part of housing portion 78
seen in FIG. 16 is located between the venous and arterial lines 72 and
74 and pinches the lines together with the clamping levers 76 when
closed.

[0116]FIG. 18 illustrates the venous and arterial line clamp subassembly
70 less a housing 77 shown in FIG. 17, in which clamps 76 are in the open
position. Subassembly 70 includes bellows 80 that hold clamps 76 open
during normal operation. Subassembly 70 also allows for an Allen wrench
82 with a T-handle 84 to be used to operate a worm gear 86 that is
coupled operably to a cam 88, which cooperate to manually open both the
venous and arterial line clamps 76 if need be. In an alternative
embodiment, subassembly 70 includes dual worm gears and a split cam, so
that the venous and arterial line clamps 76 can be manually operated
independently. FIG. 19 illustrates the placement of the T-handle Allen
wrench 82 with respect to instrument 20 when the venous and arterial line
clamps 76 are operated manually. In one embodiment, system 10 causes an,
e.g., red, flag (not illustrated) to protrude when the clamps 76 have
been opened manually. The flag retracts when the manual override is not
engaged.

[0117] FIG. 20 illustrates an exploded view of the door assembly 90 taken
from inside instrument 20. A pair of bellows or bladders 92a and 92b
pushes a plate 94 having a gasket 96 to press the cassette 40 (not seen
here) against the disposable interface 50 (not seen here). A space
between bladders 92a and 92b is provided to accommodate the inductive
heater coil 26 extending from disposable interface 50. Alternatively,
instrument 20 provides a single bellows (bladder) to press cassette 40
against the disposable interface 50, which has an internal opening to
accommodate heater coil 26 extending from disposable interface 50.

[0118] In an alternate failsafe embodiment (not illustrated), the bellows
92a and 92b are replaced by a cavity with a diaphragm that is connected
sealably to front pressure plate 18. Springs are located between front
pressure plate 18 and the back wall of the cavity and press cassette 40
against disposable interface 50, except when a vacuum is present within
the cavity. In the alternative embodiment, system 10 can also introduce
positive pressure into the cavity to increase the sealing force.

[0119]FIG. 21 illustrates system 10 with the door cover 98 (FIG. 20)
removed. Pneumatic lines 102a and 102b to bellows 92a and 92b,
respectively, are shown teed together before exiting door 18 through a
hollow hinge 104. A vertical metal bar 106 completes a circuit for the
inductive heater transformer primary coil 26 when the door 18 is closed
against interface 50 of instrument 20. FIG. 22 is also shown with door 18
removed to illustrate the inductive heating system including transformer
coil 26 and a wave-shaped disk or disks 108 located in disposable
cassette 40, which form a secondary coil that heats dialysis fluid due to
i2R losses. FIG. 23 removes cassette 40 to show inductive heater 100
more clearly. Heater 100 transfers energy from the inductive coil of the
transformer 26 into wave washers 108a and 108b that are located within
cassette 40. Washers 108a and 108b in turn heat dialysate as it flows
through cassette 40.

[0120]FIG. 24 illustrates the front of the instrument 20 with door
assembly 90 and device housing hidden to expose a mechanism 110 that
extends and retracts triple peristaltic pump race 46. Mechanism 110
includes four idler gears 112 that tie geared triple cams 114 together to
move race 46 to extend (towards tubing 44) and retract (from tubing 44)
smoothly. Mechanism 110 is configured such that race 46 extends towards
tubing 44 only after door 18 is closed and latched to preclude the
operator from being exposed to any moving components. The centers of pump
heads 22 are aligned to provide clearance between the pump heads and
triple race 46 when the race is retracted.

[0121]FIG. 25 illustrates the backside of the retractable triple
peristaltic pump race 46 and mechanism 110 for moving race 46. Cams 114
are located at each end of race mechanism 110 and race 46. A middle cam
114 is also provided. Each idler gear 112 (FIGS. 24 and 27) includes a
shaft 113 that transmits rotational motion from the idler gears to all
three cams 114 simultaneously. Cams 114 each include lobes 116 that
rotate simultaneously and in concert within large rounded end slots 118
to simultaneously and evenly extend and retract race 46. Shafts 113 of
idler gears 112 (FIG. 24) maintain the horizontal orientation of the
peristaltic pump race 46 as the race moves up and down.

[0123]FIG. 27 illustrates molded support bosses 124 secured to instrument
20 that support shafts 113 of the idler gears 112 and support the shafts
115 of cams 114 on one end. A bar (not shown here but shown in FIG. 71),
which mounts to bosses 124, supports the shafts 113 of gears 112 and
shafts 115 of cams 114 on their other ends. A motor (not illustrated)
drives cams 114, which operate the retractable pump race 46, and is
attached to any of the shafts 115 of any of cams 114. Attaching the motor
to the shaft of center cam 114 may be preferred so that clearance in the
gear train is symmetric with respect to outer cams 114.

[0124] FIGS. 28 and 29 illustrate that system 10 includes a crank 130 that
is connected to the blood pump head 22 to operate the head manually.
Manual return of the blood contained within the extracorporeal circuit is
necessary in the event of a failure of system 10 or after an extended
power failure. It is typically necessary to manually operate the venous
and arterial line clamps 76 (from a failed closed state) before being
able to return the blood in the extracorporeal circuit to the patient.
FIG. 29 also illustrates that door 18 in one embodiment defines an
opening or aperture 132 through which manual crank 130 for the blood pump
22 can be inserted with the door closed. Crank 130 includes a large
gripping handle 134 and crankshaft 136, which is sufficiently long to
allow the user to easily turn blood pump head 22. In an alternate
embodiment, manual crank 130 is built into the door assembly 90 and is
accessible to engage pump head 22 when door 18 is opened and hinged away
from machine interface 50.

[0125] As seen in FIG. 30, in one bag management embodiment, system 10
prompts the user initially to fold up all of bag shelves 16 except for
the bottom shelf 16. The user is then able to break a peel seal of a dual
chamber bag (if used), place the first solution bag 140 on bottom shelf
16 and connect the bag to the bottom supply line 38e extending from
disposable cassette 40, as shown in FIG. 31. When shelf sensors 138
detect that the bag has been placed onto first shelf 16 and that the peel
seal 142 has been broken, system 10 prompts the user to place a second
bag 140 on the second lowest shelf 16, and so on. System 10 continues to
prompt the user to place solutions bags 140 onto shelves 16 and connect
the bags to supply lines 38 until all of shelves 16 are filled, as shown
in FIG. 32.

[0126] As shown in FIG. 32, a peel seal 142 of dual chamber bag 140
present on the top shelf 16 is not broken, a condition which sensors 138
can sense, causing system 10 to instruct the user to break peel seal 142
before continuing with treatment. One such sensor arrangement and peel
seal open check is described in U.S. Patent application Ser. No.
11/773,742, entitled "Mobile Dialysis System Having Supply Container
Detection", filed Jul. 5, 2007, assigned to the assignee of the present
disclosure, the pertinent portions of which are incorporated herein
expressly by reference. FIG. 33 illustrates all solution bags 140 with
peel seals 142 broken, such that treatment can continue.

[0127] FIG. 34 illustrates one embodiment for the placement of the
capacitive sensors 138 that detect the presence of the solution bags,
whether peel seal is broken, and perhaps even whether the same solution
is present in each bag 140. Other sensors or combinations of sensors can
be used alternatively, including optical sensors, inductive sensors, bar
code readers, radio frequency identification ("RFID") tags and cameras.

[0128]FIG. 35 illustrates a luer connection assembly 144, which is
located on an end of a heparin line 146, which in turn is connected to
disposable cassette 40. A heparin syringe 148 ranging in size from ten
milliliters to sixty milliliters, can be connected to luer connection
assembly 144 of the disposable set and is inserted with the plunger 150
pointing down into a syringe pump 152 as shown in as shown in FIG. 36.
The luer connection assembly 144 is then rotated to lock the syringe in
place as shown in FIG. 37. Syringe 148, for sizes larger than 30
milliliters, is inserted with the plunger 150 pointing down into a
syringe pump 152 as shown in as shown in FIG. 38. The integral grip 149
on the larger heparin syringes is rotated forty-five degrees to lock the
syringe 148 into the syringe pump 152 as shown in FIGS. 37 and 38 versus
grip 149 shown in FIG. 36.

[0129] Syringe pump 152 is shown in more detail in FIG. 39. Pump 152
includes a stepper motor 154, gears 156, guide rails 158 and a concave
push plate 160 that self-centers on the end of the syringe plunger 150.
Air exits syringe 148 above the heparin and is purged during the priming
of the extracorporeal circuit because syringe 148 is inverted for use.
Stepper motor 154 increments 0.9 degrees per step in one implementation.
Pump 152 and assembly 144 are sized to accept nearly any size of syringe
148. The user inputs the syringe stroke length and syringe stroke volume
into system 10. System 10 can thereafter determine the volume of heparin
to be delivered.

[0130] Smaller syringes 148 are visible through a window 162 in the side
of the pump as shown in FIG. 40. Larger syringes housings are visible
since they are not inserted into syringe pump 152 and remain outside of
instrument 20 as illustrated in FIG. 38. Should a saline or dialysate bag
leak, or be spilled, onto instrument 20, the liquid could flow into the
heparin pump and out the opening in side window 162 but would not flow
inside the instrument, where the fluid could damage instrument 20.

[0131] FIGS. 41 and 42 illustrate that heparin line 146 passes through an
air bubble detector 164 to cassette 40. System 10 introduces heparin into
the patient's blood stream at the outlet 166 of the blood pump just
before the blood passes into the dialyzer. The internal volume of the
heparin line is essentially that of a very small diameter tube of minimum
length. A diaphragm actuated pinch valve 165 (plunger only shown in FIG.
41), which does not add to the internal volume of the heparin line, can
be provided to block the flow of heparin to cassette 40.

[0132]FIG. 43 illustrates a support rod 168 that collapses into
instrument 20 when not in use. Support rod 168 supports a saline bag 170
that is used for priming system 10 and rinsing blood back to the patient
at the end of the therapy. Alternatively, rod 168 is detachable from
instrument 20 when not in use.

[0133] FIGS. 43 and 44 illustrate that saline line 172 enters instrument
20 adjacent to the entry of heparin line 164 (see also FIG. 41). FIG. 45
illustrates that two saline flow control valves 174a and 174b are located
on each side of blood pump tubing loop 44. The center port from each of
the valves feeds directly into blood flow into, or coming from, the blood
pump as shown in FIG. 46. The third saline valve 174c is located on the
backside of cassette 40 as seen in FIGS. 45 and 46 and is positioned to
put saline directly into a venous air separation (drip) chamber 176. The
saline valve 174a on the blood pump outlet, and the saline valve 174b
leading to dialyzer 36, are opened sequentially to gravity prime the
arterial blood line and the venous drip chamber 176 as illustrated later
in FIG. 54.

[0134] As seen in FIG. 47, a normally evacuated dialyzer inlet line
pressure transducer interface 178 is pressurized so that it operates as a
flow control valve, preventing saline from backflowing into the dialyzer
or filter 36. The gravity head from the saline bag causes saline to flow
into the blood circuit and into the reversed rotating pump inlet 180 (the
outlet under normal operating flow) when saline valve 174a is opened. The
reversed flow blood pump head 22 draws saline from the saline bag and
pumps it through reversed flow outlet 182 (the inlet under normal
operating conditions) and down the arterial line 186.

[0135] As seen in FIG. 48, the venous line 184 and arterial line 186 are
connected in series during priming so that air is purged from both lines
via venous line drip chamber 176 shown in FIG. 49. Standard connections
188 (FIG. 48) can be used to connect the venous line 184 and arterial
line 186 in a closed loop. Gravity prevents air from being drawn from the
saline bag as long as the bag contains saline. Saline flows slowly into
the venous air separation chamber 176 in a "reverse" direction (from
normal blood flow) during priming.

[0136] In FIG. 49, the inverted-U shaped venous air separation chamber 176
has a vent port 190 located at its top, so that air can gather there and
be vented to the drain. FIG. 50 shows a valve 196 located on the opposite
side of the cassette 40 from vent port 190, which is opened whenever air
needs to be vented from the chamber. A second vent valve 192 also shown
in FIG. 50 can be placed optionally in series with first vent valve 196
and operated sequentially so that predetermined volumetric increments of
air can be vented from system 10 to a controlled vent volume 194 shown in
FIG. 51. As seen in FIG. 51, port 190 connected to the center of the
cassette-based diaphragm valve 196 communicates with air separation
chamber 176 so that the "dead" volume needed for these apparatuses is
minimized. Valve 196 seals well against the pressure present in the
venous air separation chamber. Saline bags can be replaced during a
therapy since they can be primed directly into the drip chamber 176 using
the third saline valve 174c (FIG. 49).

[0137]FIG. 52 is a schematic of one embodiment of a fluid management
system associated with the disposable set. In general, the fluid
management system includes a blood circuit 210 and a dialysate circuit
220. System 10 operates the disposable set to provide the hemodialysis
therapy. Set 200 of Figs. 53A and 53B illustrates an embodiment of a
disposable set 200 operable with system 10. Disposable set 200 includes
cassette 40, filter 36, pump tubes 44, supply tubes 38, balance tubes
202, arterial line 184 and venous line 186, etc., discussed herein.

[0138] Once disposable set 200 has been loaded into the hemodialysis
system 10, dialysate bags 140 have been connected, the saline bag 170
(FIG. 43) has been connected and the heparin syringe 148 has been loaded,
system 10 primes itself automatically starting with the blood side
circuit. The heparin pump plunger 150 is moved forward until heparin is
detected by heparin line air detector AD-HL shown in FIG. 52. Heparin
valve V-H is then closed. Next, saline is flowed from the saline bag 170
into the blood side circuit 210 as illustrated in FIG. 54, first through
valve V-SA and then through valve V-SDC. A level sensor L-ATB in the AIR
TRAP drip chamber detects saline flow into the drip chamber 176 and
determines when to close valves V-SA and V-SDC.

[0139] As shown in FIG. 55, the post pump blood valve V-PPB is then
closed, V-SV is opened and PUMP-Blood pumps saline in a reverse flow
direction. Pressure sensor P-VL and level sensor L-ATB are used to
determine when to open air vent valves V-AVB-P and V-AVB-S. The blood
pump pushes the saline backwards down the arterial line and into the
venous line. When saline reaches the venous air separator (drip chamber
176), the air will be separated from the fluid and will be discharged
into a drain line 206 through vent valves V-AVB-P and V-AVB-S until the
air separation chamber 176 is flooded with saline.

[0140] Next, as seen in FIG. 55, saline is flowed up into the bottom of
dialyzer 36 and up through its hollow fibers. Valve V-PPB is controllably
opened so that the air that exits the top of the dialyzer 36 flows into
the priming loop, becomes separated in air trap 176 and discharged to
drain 206. Saline is also flowed through pours of the fibers of dialyzer
36 to fill the housing of dialyzer 36. System 10 monitors the pressure in
the venous line using pressure sensor P-VL to maintain the blood side
circuit 210 at a controlled pressure during priming.

[0141] As seen in FIG. 56, spent dialysate pump, PUMP-DS and valves V-DS,
V-BI-S1, V-BI-SO and V-DD vent air from the dialyzer housing to drain
206. Valves V-DI-VEN, CK-VEN, V-DI-FIL, V-DI-PRE and CK-PRE are opened
controllably to allow a predetermined volume of saline to be pushed into
the dialysate circuit 220, purging air from associated dialysate lines. A
second saline bag 170 can be replaced during a therapy by selecting
"replace saline bag", causing the saline line to be primed automatically
into the air trap 176.

[0142] As shown in FIG. 56, dialysate valve V-DB1 that is associated with
the dialysate bag on the top shelf is opened so that dialysate can flow
into the inlet of dialysate PUMP-DF. PUMP-DF pushes the dialysate through
the inline fluid heater and into a dialysate side air trap 208. Dialysate
flows out the bottom of the air trap 208, through valve V-FI and into
balance tube B2, through valve V-B2-FI, pushing fluid out the other side
of balance tube B2. The fluid exiting the other side of balance tube B2
flows through valve V-B2-SO and into the dialysate recirculating circuit
203 through valve V-DR. The recirculating circuit 223 tees into the
supply line circuit 205 at the inlet to PUMP-DF. Pump-DS is operating at
the same time drawing air, dialysate and/or saline from the blood side of
the dialyzer, though the dialysate side of the dialyzer, into the
remainder of the dialysate circuit. PUMP-DS pushes the fluid through
valve V-B1-SI and into balance tube B1, pushing fluid out the other side
of balance tube B1. The fluid exiting the other side of balance tube B1
flows through valve V-B1-FO and valve V-DI-FIL into the dialysate side of
the dialyzer 36.

[0143] FIG. 57 is similar to FIG. 56 except the roles of balance tubes 202
B1 and B2 are reversed. As fluid enters the dialysate circuit 220, the
pressure in the circuit increases, forcing air to be discharged under
pressure to drain line 206 through open vent valves V-AVD-P and V-AVD-S.

[0144]FIG. 58 illustrates balance tubes 202. Instrument 20 includes pairs
of optical sensors (not shown) operable with balance tubes 202 to
determine an end of travel of a separator 212 located within each balance
tube 202. The optical sensors in one embodiment are reflective, so that
an emitter and receiver of each sensor can be on the same (e.g.,
non-door) side of balance tube 202. The sensors alternatively include
emitters and receivers located on opposite sides of balance tubes 202.
Outlets 214 on both ends of both balance tubes 202 are at the balance
tube tops when mounted for operation as shown if FIG. 58, so that air
will pass through the balance tubes and not become trapped in the tubes
as long as system 10 is level. Mechanical stops 216 limit the movement of
separators 212 to that visible to the optical sensors.

[0150] FIG. 64 illustrates one embodiment for recirculating fresh
dialysate through Fluid Heater and recirculating circuit 223 and balance
tubes B1 and B2 to remove UF. In FIG. 64, pump-DF pumps fluid in a loop
that includes Fluid Heater since valve V-DBY is open. Valve V-FI is
closed so no fresh dialysate is delivered to balance chambers 202.
Pump-DS pulls spent fluid from the dialyzer 36 through valve V-DS and
pushes the spent fluid through valve V-BI-SI and into the right side of
balance tube B1. Fresh fluid then flows from the left side of balance
tube B1 through valves V-BI-FI and V-B2FI and into the left side of
balance tube B2. Spent fluid then flows out the right side of balance
tube B2 through valves V-B2-SO and V-DD and into the drain line. In this
manner, a volume of spent fluid is sent to drain 206 without a
corresponding volume of fresh fluid delivered from supply bags 140 to
either balance chamber B1 or B2.

[0151]FIG. 65 illustrates one embodiment for closing venous line clamp
V-VLC, opening a saline valve V-SA and rinsing back the arterial line
184.

[0152] FIG. 66 illustrates one embodiment for closing arterial line clamp
V-ALC, opening a saline valve V-SA and rinsing back the venous line 186.

[0154] All or most all of the valves, pressure sensors, level sensors,
etc., can be removed without disassembly of subassembly 250. The
inductive heater mechanism 26 and bellows bladder 252 (different from
bladder 92 above) require removal of internal module 260. To this end,
four screws 266, each with a spring 268, fix a housing 270 of subassembly
250 to internal module 260. Internal module 260 can be unbolted from
screws 266, so that springs 268 push internal module 260 forward and out
of the housing 270. Power and control connections (not shown) to
subassembly 250 are also disconnected to remove internal module 260
completely.

[0155] As seen additionally in FIGS. 68 to 70, four springs 268 on the
backside of subassembly 250 retract the internal interface module 260
when bellows bladder 252 is not pressurized by pushing screens away from
housing 270 and pulling interface module 260 along with the screws. When
the bellows bladder 252 is pressurized, internal module 260 is pushed
forward and applies pressure to cassette 40, pushing the cassette against
a door gasket, which seals fluid pathways on both the front side and the
rear side of the cassette 40. The membrane gaskets 256 on the internal
module 260 mate up against the faceplate 50 of the interface module 250.
The faceplate 50 is configured so that it can support a vacuum between
the cassette sheeting and pressure sensors, liquid level sensors, etc.,
bringing the sensors into intimate contact with the cassette sheeting and
the fluid on the other side of the sheeting. System 10 is also configured
to port a vacuum between the cassette sheeting and the thin sections of
the membrane gasket 256 above the valves. This vacuum can be used to
detect holes, tears or slits in the cassette sheeting before, and during
a therapy.

[0156]FIG. 71 is a view of the backside of system 10 with the cover
removed. The open space houses interface assembly 250, hinged shelves 16,
peristaltic pump motors 120 a pneumatic pump, a power supply, battery and
electronics that operate the system.

[0157]FIG. 72 illustrates system 10 operating alternatively with an
online dialysate generation system 300. System 300 generates dialysate
online or on-demand, eliminating bags 140, shelves 16 and multiple supply
tubes 38. A single supply tube 38 feeds from generation system 300 to
instrument 20. Water inlet line 302 and drain lines 304 lead to and from
generation system 300, respectively.

[0158] FIGS. 73A, 73B and 74 illustrate a cassette 40 diaphragm valve
chamber configuration 280, which solves an inherent problem with
diaphragm valves have when attempting to seal against downstream pressure
because the pressure that is trying to seal off the valve is acting on an
area that is just slightly larger than an area upon which the downstream
pressure is acting. The difference between the two areas is the area
defined by the top of the "volcano". Also, if the downstream fluid volume
is completely fixed when the diaphragm valve closes, further movement of
the diaphragm is prevented after the initiation of the seal because of
the incompressibility of the trapped fluid. The result is that the
downstream pressure equals the valve sealing pressure. Diaphragm valve
configuration 280 provides a diaphragm valve that can seal against both
upstream and downstream pressure via a connection of two diaphragm valve
chambers 282 and 284 placed in series. Diaphragm valve chambers 282 and
284 are connected fluidly via a compliance chamber 286, which allows
sheeting seals 288 of the cassette sheeting to close around respective
volcano ports 290 of both valve chambers 282 and 284.

[0160] FIG. 73A shows a cross-section of two diaphragm valve chambers 282
and 284 with an integral compliance chamber 286, wherein the diaphragms
can readily close seals 288 to ports 290. Here, a vacuum is applied to a
lower diaphragm 289 at the compliance chamber 286. Diaphragm 289 is
flexible and has a relatively large cross-sectional area to absorb the
kinetic energy created by a pneumatic valve actuator applying a positive
pressure Pa, such that the positive sealing pressure applied to one valve
chamber 282 or 284 is much less likely to harm an existing seal of a
fluidly connected upstream or downstream valve chambers. The negative
pressure pulls sheeting 288 down around ports 290 and allows valve
chamber 282 or 284 to be sealed against the backpressure applied by its
own sealing pressure (around the outside of port 290) plus backpressure
from a fluidly connected upstream or downstream valve chamber residing up
through the center of port 290.

[0161] Compliance chamber 286 as seen in FIG. 73B is configured a little
bit differently and uses a portion of the membrane or sheeting seals 288
of valve chambers 282 and 284 to provide a compliant material covering a
relatively large cross-sectional area 292 of chamber 286. Here, a vacuum
applied to sheeting 288 at chamber 286 negates the positive pressure Pc
applied around the outside of ports 290 and expands the relatively large
area 292 of the valve seal sheeting, pulling sheeting 288 down around the
outside of port 290. The configuration of FIG. 73B is advantageous in one
respect because positive and negative pressures are applied to the same
side of the cassette at chamber configuration 280, such that associated
pneumatics can be located on a single side of the cassette.

[0162] By changing the pressure seen at compliance chamber 286 from a
positive pressure when the valve chambers 282 and 284 are open to a
negative value after the valve chambers results in that only the liquid
side center of the volcano port 290 is exposed to high positive pressure.
The liquid annular area of valve chambers 282 and 284 on the outside of
volcano ports 290 sees the applied vacuum, which allows the air sealing
pressure on the outside of the cassette to seal against backpressures
that would have otherwise forced it open. This allows valve chambers 282
and 284 to seals well in both upstream and downstream configurations.

[0163] In one example, suppose the total seal area of valve chambers 282
and 284 is one square inch and that the sealing area at the top of
volcano port 290 is 0.1 square inch over the volcano. A positive ten psig
air pressure would then apply an external force of 10 lbs to the entire
valve chamber 282 or 284. A backpressure on the annular fluid side of the
associated port 290 from the applied ten psig pressure plus a
backpressure the backpressure up through the center of port 290 from a
downstream sealed valve would exert almost the same opposite "unsealing"
force of ten pound (only difference would be the small annular area of
port 290 at the top, which is a function of the port wall thickness and
the diameter of the tube), resulting in a potentially leaky valve chamber
282 or 284. A higher positive pressure, e.g., twenty psig, could be
applied to valve chamber 282 or 284 forcing sheeting 288 to seal to port
290 against the 10 psig backpressure, however, the noise generated to
create the twenty psig air pressure could objectionable to the user.
There would also be no redundancy in the different valve pressures.

[0164] Back to back valve chambers 282 and 284 of FIGS. 73A and 73B, on
the other hand, separated by an applied negative pressure, e.g., 5 psig
vacuum, both seal independently well. The ten psig air pressure would
still apply 10 lbs external force to seal both valves 282 and 284,
however, the 10 psig pressure at the center of the volcano port 290 and
the -5 psig pressure on the annular area around the volcano would apply a
total pressure of ten psig*0.1 sq in+(-5 psig)*0.9 sq in=-3.5 lbs. The
net force to close the valve would be 13.5 lbs so that valve would seal
very well.

[0165] It may be possible to not use a separate vacuum and instead rely on
the expansion of the flexible part of the compliance chamber 286 to
absorb energy from the backpressure from one valve chamber 282 or 284
applied to the other valve chamber 282 or 284. Here, apertures 283 allow
the pressurized fluid inside chambers 282 and 284 and around ports 290 to
communicate with fluid inside compliance chamber 286 and expand diaphragm
289 or sheeting area 292, allowing the backpressure around ports 290 to
dissipate.

[0166] Valves V-DI-PRE, CK-PRE, V-DI-VEN and CK-VEN in FIG. 52 (and other
flow schematics) and valve chambers 282 and 284 of valve configuration
280 of cassette 40 shown in FIG. 74 are constructed as shown
schematically in FIGS. 73A and 73B and can seal against higher pressure
in either direction. That is, not only does compliance chamber 286 serve
to not disrupt an existing upstream or downstream first valve chamber
closure when a second valve chamber in fluid communication with the first
valve chamber is opened, compliance chamber 286 also aids in the closure
of a first valve chamber when a second valve chamber in communication
with the first valve chamber (upstream or downstream) has been closed
previously, which could otherwise create positive fluid pressure against
which the closure of the first valve chamber would have to fight.

[0167] FIG. 75 illustrates that system 10 in one embodiment includes a
wide pump head 22 that drives two dialysate pump segments 44 to mix two
solutions in a ratio that is approximately equal to the ratio of the tube
inside diameters squared (mix ratio=(ID1/ID2)2), assuming the wall
thicknesses of tubes 44 is the same. For a 1:1 mix ratio, consecutive
segments of tubing from the same roll of tubing can be taken to provide
segments of the same wall thickness and good mixing accuracy. Mixing
accuracy is optimized because the inlet pressure on the supply lines is
controlled within about four inches of water column by the bag manager,
the tubing inner diameter is controlled during the manufacture of the
disposable set, the pump race diameters are the same and the pump
actuator rotational speed is the same for the parallel tubing segments.
System 10 also ensures that an initial supply fluid temperature of each
of the different dialysis fluids in tubes 44 is within a few degrees of
each other.

[0168] It should be understood that various changes and modifications to
the presently preferred embodiments described herein will be apparent to
those skilled in the art. Such changes and modifications can be made
without departing from the spirit and scope of the present subject matter
and without diminishing its intended advantages. It is therefore intended
that such changes and modifications be covered by the appended claims.